Coated unspun fibers and process of producing pile fabric therewith



COATED UNSPUN FIEERS PRGCESS F PRGDUQENG PETE FABRIC TI-IEREWITH Henry Ewing, Spondon, near Derby, England, assignor to British Celanese Limited, a corporation of Great Britain No Drawing. Application August 25, 1950, Serial No. 181,585

Claims priority, application Great Britain September 7, 1949 12 Claims. c1. 117-17 This invention relates to fibres and especiallyto a treatment directed to reduce the tendency to self-adhesion in fine, unspun fibres of artificial textile material. In this specification fine means of denier not greater than 20 and fibres includes continuous filaments.

In some textile processes, for example, in the production of suedette and other pile fabrics by causing short staple fibres to adhere to a fabric coated with an adhesive, the problem arises of breaking up a flock of short staple fibres into individual fibres. Thus, for example, in the manufacture of pile fabrics of the kind referred to, one method is to feed a flock of short fibres (e. g. fibres from 1 mm. or less to about 5 mm. in length) into the vicinity of the adhesive coated surface of a fabric while the fabric is travelling through an alternating electric field. This field serves to separate and orient the fibres and to impel them on to the adhesive surfaces. Other methods of making such pile fabrics involve blowing the flock and distributing it with the aid of a beater. In operating those methods a marked tendency is observed for the fibres to stick together, so that they tend to be distributed over the adhesive coated surface not as individual filaments uniformly spaced apart, but as clusters of several filaments. I have found that this tendency to self-adhesion is con nected with the fact that at some stage in the manufacture of the fibres the fibre-forming material has been lubricated (usually with an oil) to facilitate processing. None of the recognised scouring treatments commonly applied to remove residual lubricants was found efiective in removing this tendency to self-adhesion. Thus, even after the flock had been scoured at 60 C. with an emulsion of xylene in Turkey red oil and washed and dried, the selfadhesion was still sufiiciently marked to cause considerable clustering together of filaments in the electric field. Attempts to extract the lubricant with benzene and with ether gave some improvement and extraction with cyclohexanane gave a very considerable improvement. This however is a somewhat costly operation, and attention was further directed to finding a means of improving the performance of the fibrous material in processes such as those referred to above, without recourse to extraction by solvents.

I have now found that very great reduction in the tendency to self-adhesion, and correspondingly better performance in the processes referred to, can be obtained by applying to the surface of the fibrous material. an inert,

water-insoluble, finely divided solid substance preferably in aqueous suspension.

The solid substance applied should preferably have a hardness of at least 1 on the-Mobs scale and be non-thermoplastic. Preferably it should also bewhite or colourless. The particle size of at least 90% by weight of the solid substance should be less than 100 microns, e. g., up.

to 50 microns, and preferably not greater than microns. It may be less than 1 micron, e. g. 0.1 to 1 or. 0.51 to 1 micron. A very useful range of particle size is l to 10 microns. These various requirements. can be met by a asessse Patented Sept. 10, 1957 choice of suitable inorganic substances. The best results have so far been obtained using finely divided precipitated silica. Excellent results have also been obtained with finely divided magnesium oxide. Talc and precipitated calcium carbonate have given somewhat less improvement. Other substances that can be used include barium sulphate, gypsum, china clay, and aluminum oxide. Diatomaceous earth is of too large a particle size to give the best results although some improvement may be obtained from its use especially with the coarser fibres, e. g. fibres of denier 10 to 20. The presence in the aqueous suspension of dispersing agents, or of agents adapted to fix the solid substance on the fibre, is unnecessary and in general undesirable. The suspension may contain, for example, 2 to 5% of the solid substance based on the weight of the flock. The concentration of the silica or other solid substance may be, for example, between about 0.5% and 1.5% by weight. More concentratedsuspensions give the desired effect, but besides being wasteful, tend to leave a noticeable amount of the solid substance on the fibre. The amount of the solid substance left on the-fibre is preferably kept below about 6%, for example, 3 to 5% or better still 0.5 to 3%. In general, less of the solid substance need be retained to give the desired improvement, the lower the amount of residual lubricant. To avoid affecting the properties of the pile fabrics or other products formed from the flock, it is desirable to use as little of the solid substance as is consistent with giving the desired reduction in self-adhesion.

Substantial difference in electrical properties, in particular dielectric constant, between the fibre and the solid substance makes possible the removal of excess of the solid substance by exciting the treated flock in the alternating electric field. Similarly a pronounced diiference'i-nspecific gravity enables some separation to be effected by blowing. The amount of solid material retained may also be reduced by Washing. It. is preferred however to apply the solid substance in an aqueous suspension of such concentration that after separating the treated material from the bulk of the suspension and drying it the amount of solid substance retained is within the specified" limits.

The following examples illustrate the invention:

Example 1 The flock treated was composed of fibres of length 1 mm. made. from cellulose acetate artificial silk waste of denier 4.5 which in the course of its production had been lubricated with a lubricant comprising white parafiin and palm-kernel oil. On subjecting this flock to an alternating electrical field such as is used in electro-deposition of short fibres on an adhesive-coated fabric, the tendency of the fibres to self-adhesion was very marked, and the movement of the two clumps of fibres formed-under the influence of the field, was very sluggish. A portion of the flock after being scoured for 15 minutes at 60 C. in-

of by weight of particles of size 1 to 10 microns.

The bath volume was 15: 1. Thefibre treated in this way and dried, showed a much. reduced tendency to clustering, and correspondingly better performance in the electro-coating process.

Example 2 The process was carried out as in Example I but,

The amount of'calcium carbonate. left on the fibre was howevensomewhat high ,.viz.' 1.3

The process was carried out as in Example 1 but using as the finely divided substance precipitated silica of the same particle size. Excellent results were obtained, with a retention of silica on the fibre of only 0.5%.

Example 4 The process was carried out as in Example 3 but substituting for the silica magnesium oxide of about the same degree of fineness as the silica. A similar improvement to that in Example 4 was obtained but in this case with retention on the fibre of about 2% of the magnesium oxide.

Example 5 The flock used was of regenerated cellulose made by the viscose process and of denier 4.5 and average fibre length 1 mm. The tendency to self-adhesion in this flock was so great that the clusters of fibres hardly moved in the alternating electric field. The flock was scoured and treated with an aqueous suspension of silica as described in Example 3. The amount of silica left on the fibre was 0.8% of the weight thereof. By this treatment the tendency to self-adhesion was so reduced that the performance of the fibre in the electric field was excellent.

In a further series of trials with the two kinds of flock referred to, the concentration of the suspension of silica used was reduced to 2.5% keeping the bath volume the same. Excellent performance in the electric field was obtained with even less retention of silica by the material. Trials were also carried out on both kinds of flock, in which the improvements resulting from the various treatments were assessed by blowing the flock through a nozzle bymeans of air pressure. These trials showed improvements in reduced self-adhesion of the same order as were shown by the trials in the electric field.

The treatment according to the invention is of particular importance when applied to a flock of very short fibres for example, from 0.5 mm. to about 5 mm. in length, and especially from 1 to 2 mm. The treatment greatly facilitates the use of such a flock in the manufacture of suedette and other pile fabrics of the kind referred to above. The treatment of the invention may also be used with advantage in making staple fibres, whether long or short, for example by grinding, cutting, or breaking methods. Thus, for instance, the treatment may be applied to continuous filament yarns, especially substantially twistless yarns, or to rovings, or to waste yarn, before or continuously with, conversion into staple fibre. In this way the conversion to staple fibre may be much facilitated. The invention includes the application of silica or other suitable solid substances in such processes together with an antistatic agent. The invention may also be applied in the manufacture of carpets, rugs, and upholstery pile fabrics, where the treatment reduces not only self-adhesion between the fibres but also the tendency (due also to contamination with lubricant) to pick up dirt.

The fibre treated may be, for example, of regenerated cellulose, or of a cellulose ester or ether, for example cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate-propionate, cellulose acetate-butyrate, ethyl cellulose or benzyl cellulose. The process of the invention is also applicable to the treatment of fibrous material composed of artificial proteinaceous fibres or of synthetic polymers. Among the synthetic polymers mention may be made of condensation polymers such as polyhexamethylene adiparnide, polyethylene terephthalate, and polyaminotriazole and of addition polymers such as polyacrylonitrile and the co-polymers of vinyl chloride with vinylidene chloride, vinyl chloride with acrylonitrile,

4 vinylidene chloride with acrylonitrile, and acrylonitrile with methacrylonitrile.

Having described my invention, what I desire to secure by Letters Patent is:

l. Unspun fibres of artificial textile material of length not greater than 2 mm. and of denier 3-15, said fibres being coated with 0.5-3% of their weight of silica in the form of particles of which at least by weight are of diameter between land 10 microns.

2. Unspun fibres of cellulose acetate of length not greater than 2 mm. and of denier 315, said fibres being coated with 0.5-3% of their weight of silica in the form of particles of which at least 90% by weight are of diameter between 1 and 10 microns.

3. In a process in which a pile fabric is made by electrodeposition of unspun fine fibres of artificial textile ma terial on an adhesive-coated fabric under the action of an alternating electric field, the step of forming said pile from fibres which are coated with 0.5-3% of their weight of a substantialy white or colourless water-insoluble solid, non-thermoplastic, inorganic, inert substance having a hardness of at least 1 on the Mohs scale, in the form of particles of which at least 90% by weight are of diameter between 1 and 10 microns whereby the tendency towards self-adhesion of said fine fibres is reduced.

4. In a process in which a pile fabric is made by electrodeposition of unspun fine fibres of artificial textile material on an adhesive-coated fabric under the action of an alternating electric field, the step 'of forming said pile from fibres which are coated with 0.5-3% of their weight of silica in the form of particles of which at least 90% by weight are of diameter between 1 and 10 microns whereby the tendency towards self-adhesion of said fine fibres is reduced.

5. Process according to claim 3 in which said fibers are not greater than 2 mm. in length.

6. Process for the production of pile fabrics, which comprises applying to unspun fine fibres of artificial textile material of a length not greater than 5 millimeters a substantially white or colourless, water-insoluble solid, non-thermoplastic, inorganic, inert substance having a hardness of at least 1 on the Mohs scale, in the form of particles of which at least 90% by Weight are of diameter between 1 and 10 microns whereby the tendency towards self-adhesion of said fine fibres is reduced, and electrodepositing said coated fibres on an adhesive-coated fabric under the action of an alternating electric field to form a pile on said fabric.

7. Process for the production of pile fabrics, which comprises applying to unspun fine fibres of an artificial organic textile material of length not greater than 2 millimeters a suspension in water of silica particles of which at least 90% by weight are of diameter between 1 and 10 microns, separating the treated material from the bulk of the suspension and drying the material to obtain fibres coated with said particles of silica, the amount of silica being 0.5 to 3% of the weight of said fibres, and electrodepositing. said coated fibres on an adhesive-coated fabric under the action of an alternating electric field to form a pile on said fabric.

8. Process for the production of pile fabrics, which comprises applying to unspun fine fibres of cellulose acetate of length not greater than 2 millimeters a suspension in water of silica particles of which at least 90% by weight are of diameter between 1 and 10 microns, separating the treated material from the bulk of the suspension and drying the material to obtain fibres coated with said particles of silica, the amount of silica being 0.5 to 3% of the weight of said fibres, and electrodepositing said coated fibres on an adhesive-coated fabric under the atcion of an alternating electric field to form a pile on said fabric. 7

9. Process for the production of pile fabrics, which comprises applying to unspun fine fibres of regenerated cellulose of length not greater than 2 millimeters a suspension in water of silica particles of which at least 90% by weight are of diameter between 1 and microns, separating the treated material from the bulk of the suspension and drying the material to obtain fibres coated with said particles of silica, the amount of silica being 0.5 to 3% of the weight of said fibres, and electrodepositing said coated fibres on an adhesive-coated fabric under the action of an alternating electric field to form a pile on said fabric.

10. Unspun fibres of artificial textile material of length not greater than 2 mm. and of denier 3l5, said fibres being coated with 0.53% of their weight of a substantially white or colourless water-insoluble solid, non-thermoplastic, inorganic, inert substance having a hardness of at least 1 on the Mohs scale in the form of particles of which at least 90% by weight are of diameter between 1 and 10 microns, said inert substance being selected from the group consisting of silica, magnesium oxide, talc, precipitated calcium carbonate, barium sulphate, gypsum, china clay, and aluminum oxide.

11. Unspun fibres of regenerated cellulose of length not 6 greater than 2 mm. and of denier 3-15, said fibres being coated with 0.53% of their Weight of silica in the form of particles of which at least by weight are of diameter between 1 and 10 microns.

12. Unspun fibres of cellulose acetate of length not greater than 2 mm. and of denier 3-15, said fibres being coated with 0.53% of their weight of magnesium oxide in the form of particles of which at least 90% by weight are of diameter between 1 and 10 microns.

References Cited in the file of this patent UNITED STATES PATENTS Bauer Oct. 9, 1951 

8. PROCESS FOR THE PRODUCTION OF PILE FABRICS, WHICH COMPRISES APPLYING TO UNSPUN FINE FIBRES OF CELLULOSE ACETATE OFLENGHT NOT GREATER THAN 2 MILLIMETERS A SUSPENSION IN WATER OF SILICA PARTICLES OF WHICH AT LEAST 90% BY WEIGHT ARE OF DIAMETER BETWEEN 1 AND 10 MICRONS, SEPARATING THE TREATED MATERIAL FROM THE BULK OF THE SUSPENSION AND DRYING THE MATERIAL TO OBTAIN FIBRES COATED WITH SAID PARTICLES OF SILICA, THE AMOUNT OF SILICA BEING 0.5 TO 3% OF THE WEIGHT OF SAID FIBRES, AND ELECTRODEPOSITING SAID COATED FIBRES ON AN ADHESIVE-COATED FABRIC UNDER THE ACTION OF AN ALTERNATING ELECTRIC FIELD TO FORM A PILE ON SAID FABRIC. 